Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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AIR SUSPENSION ADAPTER KIT
FIELD OF THE INVENTION
This invention relates generally to air suspensions for trailers such as small
utility
trailers, camper trailers and recreational vehicle trailers.
BACKGROUND OF THE INVENTION
Utility trailers are used to provide additional hauling capacity to standard
automobiles and light trucks. They often connect to such a vehicle using a
hitch, such as a
conventional ball hitch. An electrical connection, typically through a
connection to trLe
brake light power source, is employed to enable brake lights at the rear of
the utility
trailer.
Conventionally, utility trailers have a single axle on which the trailer's
wheels are
mounted. By connecting to the hitch, the trailer is then supported at three
points (the hitch
and each of the wheels.) This leaves the trailer relatively level and stable.
The axle is
typically mounted to the trailer using a set of leaf springs. This provides a
durable
suspension system that effectively spreads the weight load widely over the
chassis of the
utility trailer.
On acknowledged problem with the use of leaf springs is their inability to
vary the
stiffness of the suspension in response to differing loading weights. To
address this issue,
pnetunatic or air suspensions have been employed. The leaf spring is replaced
by a
compressible air bladder that can be variably inflated to different pressures.
The air
pressure in the bladder can be varied to accommodate different loads, and to
adjust the
stiffness of the suspension. One example of such a system is provided in US
Patent No.
6,086,276, which discloses the use of an inflatable air bladder to act as a
dampener for a
partial axle.
The use of an air bladder also offers the ability to increase the
fuiictionality of a
trailer by allowing the bed of the trailer to be lowered through deflation of
the bladder.
This effectively provides the ability to have the trailer "kneel" to allow
easier access.
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Despite the existence of air suspension trailers, the market for all small
trailers is
typically tilted towards sales of the lower cost leaf spring suspension
trailers. Often a leaf
spring suspension trailer is the first trailer that a person will purchase,
and only when a
second trailer is needed does a person consider buying an air suspension
trailer
As a well-maintained trailer often lasts a long time, many people who might be
interested in the functional advantages of an air suspension system do not
consider
purchasing a new trailer because the existing trailer is fully serviceable.
Various air-suspension systems exist, including those provided by Dexter Axle,
whose AirflexTM system is intended for use by trailer assembly and sales
companies to use
in air-suspension trailers. In conventional air-suspension systems an
expensive air bladder
is used as to dampen the vibrations encountered. As the loads placed on the
bladder are
large, the bladders must be designed to accept a large amount of compressive
force when
they are inflated without causing a blow out. This requires expensive
bladders.
Furthennore, the axle is connected to the air-suspension system using U-bolts
that are
secured through plates bolted to support arms. As the trailer is used on
rougher surfaces,
vibrations in the trailer often loosen the secure fit achieved by the U-bolts,
resulting in a
loosening of the axle, which is undesirable for a number of reasons that will
be understood
by those skilled in the art.
It is, therefore, desirable to provide a mechanism to allow owners of
conventional
trailers to obtain the benefits of an air suspension systean for existing
trailers.
SUMMA'RY OF THE INVENTION
It is an object of the present invention to obviate or mitigate at least one
disadvantage of the prior art.
In a first aspect of the present invention, there is provided an air
suspension kit for
a trailer having a fixed axle, The kit comprises first and second hanger
brackets, first and
second support anns, first and second inflatable air bladders, first and
second and an
inflation control system. The first and second hanger brackets attache to
respective first
and second side rails of the trailer. The first and second support arms
connect to the
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respective first and second hanger brackets. Each support arm has a hanger
bracket mount
point at one end, an air bladder mounting surface at an opposing end of the
arm, and an
axle recess positioned between the two ends for receiving the axle. Each of
the inflatable
air bladders connect to the air bladder mounting surface of the respective
support arm and
the respective side rail. Each bladder can be used to increase and decrease
the distance
between the respective side rail and support arm in accordance w:ith the
quantity of air
stored in the bladder. The inflation control system controls air flow into and
out of the first
and second air bladders to maintain alignment of the side rails and support
arms in a
predetennined configuration.
In an embodiment of the present invention, the kit includes a set of
instructions for
assembling the elements of the kit. The kit can further include first and
second shock
absorbers, each of the shock absorbers for connection between respective a
hanger bracket
and support arm. Each of the hanger brackets can include a side rail
attachment surface for
allowing of attachment of the hanger bracket to a side rail.
Each of the hanger brackets can also include a support arm mounting point,
which
optionally has a connection pin for connecting the support arm mounting point
of the
hanger bracket to the hanger bracket mount point on the support arm. The
connection pin
can include an alignment collar for allowing the alignment of each support arm
to its
respective side rail.
In an alternate embodiment, the axle recess on a support arm is sized to
receive tlie
axle in welded engagement. In another embodiment, the kit further includes
first and
second axle collars. The axle collars engage both the axle and the axle
recesses in each of
the first and second support arrns respectively. The axle collar is preferably
cylindrical
with an inner diameter equal to the diameter of the axle and an outer diameter
sized to fit
inside the axle recesses. The axle collar and the suppoi-t arms are preferably
fashioned
from a weldable material, and the axle collars are welded to both the support
arms and the
axle.
In a further embodiment, the inflation control system includes an air supply
for
providing a pressurized supply of air to the air bladders to inflate the
bladders. The
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pressurized air supply can be provided by an air compressor, which is powered
by a
connection to a towing vehicle battery. The presstirized supply can further
include a
pressurized tank of air that is filled by the compressor. The pressurized tank
can store
pressurized air for transmission to the air bladders. The air compressor can
be controlled
by a regulator, so that the compressor provides air to the pressurized tank
when the
pressure of the pressurized tanlc falls below a predetermined level. The
regulator can stop
the compressor from providing air to the pressurized tank when the pressure in
the
pressurized tank exceeds a second predetermined level. The pressurized tank is
preferably
connected to the air bladders through a valve opened when the alignment of the
siderails
and support arms is not in the predetermined configuration due to excess
loading of the
trailer. The valve can be a three way ball valve for inflating the air
bladders by conneetinig
them to the pressurized tank when the alignment is not in the predetermined
configuration
due to excess loading, for deflating the air bladders by connecting them to
the outside
environment when the alignment is not in the predetermined configuration due
to
insufficient loading, and for sealing the bladders when the alignment is in
the
predetermined configuration.
In a further embodiment, the trailer can be one of a utility trailer, a camper
trailer
and a recreational vehicle trailer.
Other aspects and features of the present invention will become apparent to
those
ordinarily skilled in the art upon review of the following description of
specif e
embodiments of the invention in conjunction with the accompanying figures.
BRIEF DESCRIPTION OF THE DRAWINGS
Embodiments of the present invention will now be described, by way of example
only, with reference to the attached Figures, wherein:
Figure I illustrates a conventional leaf spring suspension trailer,
Figure 2 illustrates a set of parts for an air suspension system;
Figure 3a illustrates a front view of a hanger bracket;
Figure 3b illustrates a rear view of a hanger bracket;
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Figure 3c illustrates a side view of a hanger bracket;
Figure 4a illustrates an under slung support arm;
Figure 4b illustrates a top mount support arm;
Figure 5a illustrates an assembled axle wrap from an end view;
Figure 5b illustrates an exploded axle wrap from a side view;
Figure 5c illustrates an axle wrap assembled around an axle from a side view;
Figure 6a illustrates an air bladder from a top view;
Figure 6b illustrates a cut-away of the air bladder illustrated in Figure 6a;
Figure 7 illustrates the assembly of the elements of Figure 2 to provide an
air
suspension system; and
Figure 8 illustrates a control system for determining and maintaining the
level and
air pressure in the suspension system.
DETAILED DESCRIPTION
The present invention is directed to a novel suspension. system for utility
trailers
that can be installed as an aftermarket modification for fixed axle trailers.
Reference is made below to specific elements, numbered in accordance with the
attached figures. The discussion below should be taken to be exemplary in
nature, and not
as limiting of the scope of the present invention. The scope of the present
invention is
defined in the claims, and should not be considered as limited by the
implementation
details described below, which as one skilled in the art will appreciate, can
be modified by
replacing eiements with equivalent functional elements.
Figure 1 illustrates an exemplary embodiment of a conventional trailer using
leaf
springs and a fixed axle. The trailer 50 has a hitch 52 for connecting to a
vehicle and a
load gate 54 at the opposing end. An axle 56 is fixedly mounted to the side
rails 58a and
58b by leaf springs 60a and 60b respectively. Wheels 62a and 62b are mounted
to the axle
56 to allow them to rotate freely. The leaf springs 60 serve as a suspension
by flexirig
under pressure.
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To serve as an after market modification, or as a set of elements for use in
primary
assembly, the present invention provides support for the fixed axle of the
prior art trailer
illustrated in Figure 1.
Figure 2 illustrates a set of parts that can be provided as a kit for
implementing the
trailer suspension system of the present invention in. place of the leaf-
spring suspension of
the prior art. The kit includes a pair of hanger brackets 100 (individually
referred to as
hanging bracket IOOa and 100b) for mounting in the underside of the trailer; a
pair of
support arms 102 (individually referred to as support art 102a and 102b) each
of the arms
for pivotal connection to one of the hanger brackets 100; air bladders 104
(individually
referred to as 104a and 104b), optional shock absorbers 106 (individually
referred to as
shock absorber 106a and 106b) and optional axle wraps 108 (individually
referred to as
axle wraps 108a and 108b).
The support arms 102 can be pivotally connected to the hanging brackets 100,
which serve to space the support arms 102 from the underside of the trailer.
Each of thes
support arms 102 has a mounting surface for supporting the air bladders 104.
Optionally,
the shock absorbers 106 can be used to provide a second connection between the
hanging
brackets 100 and the suspension arms 102. The shock absorbers 106 can be used
to damp
the pivotal motion between the support arms and the hanging brackets. Support
aims 102
also include a mounting recess for supporting the axle. Proper fit of the axle
in the recess
can be obtained using axle wraps 108 which adapt the diameter of an axle to
the possibly
larger diameter of the mounting recesses.
The elements of the above-described kit will now be described in fiirther
detaiil.
The assembly of the elements and the use of a control system will be discussed
following
the discussion of each element.
Figures 3a 3b and 3c show the front, rear and side vi.ews respectively of an
exemplary lianger bracket 100. Hanger bracket 100 has a top plate 110 that
allows bracket
100 to be mounted to the underside of a trailer. A front wall 112 connects
sidewalls 1114
and 116 to each other.l2ear flange 118 is connected to sidewa11114, while rear
flange 120
is connected to side wall 116. Sidewalls 114 and 116, rear flanges 118 and 120
and front
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wall 112 are all connected to top plate 110. As shown in Figure 3c,
sidewal1114 include;s
an aperture 122 (a similar aperture exists on sidewall 116 though is
unillustrated).
The aperture 122 allows for pivotal mounting of the support arm 102. The use
of an ovoid
aperture 122 allows for the use of an alignm.ent collar to align the
suspension arms so that
they are parallel to the side rails of the underside of the trailer even if
the hanging bracket
is slightly misaligned. One skilled in the art will appreciate that apertttres
of other shapes
and designs can be used without departing from the scope of the present
invention.
Figure 4a and 4b illustrate alternate embodiments of the support arm 102 shown
in
Figure 2. In Figure 4a, an under slung support arm 102 is shown. A mounting
point 124 is
provided at one end of the mounting atm 102. This mounting point is designed
for mating
with the aperture 122 on hanging bracket 100. In the illustrated embodiment,
the mounting
point 124 is an aperture that can be aligned to with aperture 122 and
connected using a
standard bolt, and alignment collars, as will be understood by those skilled
in the art.
When assembled, a pair of hanging brackets 100 each have a support arm 102
connected
to them, and the support arins 102 are connected to each other by the axle.
The axle is then
aligned with the trailer side rails, by adjusting the moiuiting point 124 in
the aperture 122
on the hanging bracket 100 using alignrnent collars. One skilled in the art
will appreciate
that the alignment process is provided to account for manufacturing and
assembl[y
variations, though a sufficiently precise manufacturing and installation
process can obviate
the need for alignment collars.
Set away from the mounting point 124 is the mounting recess 126 which mates
with the axle of the trailer. One skilled in the art will appreciate that
mounting arm 102 is
referred to as an under slung arm because it supports the axle in nnounting
recess 126 fro;m
below. At the far end of the support arm 102 from the mounting point 124 is
mount.ing
surface 128 which is designed to support the air bladder, such as bladder 104
of Figure.2.
One skilled in the art will appreciate that alternate designs of the present
invention can
change the relative positioning of the mounting recess 126 and the mounting
surface 128.
Figure 4b illustrates an alternate embodiment of support arm 102, a top mount
arm
as opposed to the under slung arm of Figure 4a. Mount point 124 and mounting
surface
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128, each with the same configuration as shown in Figure 4a is shown. However,
in this
instance, the mounting bracket is slung over the axle, so mounting recess 126
is provided
on the underside of the arm as illustrated. One skilled in the art will
appreciate that
mounting recess 126 is designed to accommodate the axle of the trailer in a
fixed
mounting. In place of the conventional bolts, a permanent mounting mechanism
is
preferably used. The axle can be bonded to the support arm through a welding
process, or
through another permanent connection. This prevents the gradual loosening that
plagues
prior art implementations that rely upon bolts.
Figure 5a illustrates the axle wrap 108 in an end view. This wrap is
cylindrical in
shape with a central aperture 130 sized to accept the existing axle of the
trailer. The
extemal surface of wrap 108 is sized to fit within the mounting recess 126.
Wrap 108 is
illustrated as being a two part assembly that forms a clamshell style
connection around the
axle. On skilled in the art will appreciate that the two part assembly
illustrated is simply Em
exemplary embodiment, one part assemblies can be used without departing from
the scope
of the present invention. A two part assembly provides ease of assembly in
comparison to
a one piece wrap when the wheels have already been fitted to an axle as is the
case in
retrofitting an existing trailer, while a one piece assembly can provide
simplicity and ease
of use for new installations. The wrap 108 can secured in the recess 126 by
welding or
another permanent binding process. Welding is employed, between the axle wrap
and the
axle, and the axle wrap and the recess, to ensure a secure and permanent bond.
Conventional air-suspension systems have attempted to move towards ease of
assembly,
which is important in an assembly line setup, and have thus avoided using
permanent
connections such as welds in favor of U-bolts with locking nuts. Though bolt
and nut
connections are relatively secure, they tend to become less secure as time
progresses as the
trailer is subjected to vibrations. Excessive vibrations, often caused by
poorly maintained
roads or unpaved surfaces, are known for loosening these connections. As the
connections
are loosened, the axle can become misaligned which increases the need for the
user to
have the trailer serviced. The use of a permanent bonding, such as a weld,
greatly
mitigates this problem at the expense of a more difficult installation.
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Figure 5b illustrates the front view of the wrap 108 in exploded form. Wrap
108 is
formed of two complementary pieces, such as wrap halves 132 and 134. The
pieces are
placed around an axle and are then welded together to form a solid piece. Once
again,
other permanent fastening mechanisms other than welding can be employed
without
departing from the scope of the present invention. Figure Sc illustrates the
assembled
halves 132 and 134 of axle wrap 108 enclosing an axle 136. As indicated above,
a weld
can be employed to fixedly connect the two halves.
Figure 6a illustrates a top view of the air bladder 104 of the present
invention. An
inflatable bladde.r 138 is arranged around a top support plate 140. The
inflatable bladder
138 receives and discharges air from inflation valve 142 which, along with
support point
144, is supported on top support plate 138.
Figure 6b illustrates the air bladder 104 from a side view. The air bladder
104 has
inflatable bladder 138, top support plate 140, air valve 142 and support point
144, as
shown in Figure 6a. The bladder is supported by base 146, which provides a
mountir.ig
point 148 for connecting the air bladder 104 to the mounting surface 128 of
the support
arm 102. The valve 142 and support point 144 are used to connect the air
bladder 104 to
the underside of the trailer. Thus, air bladder 104 is used to dampen motion
of the support
ann 102 with respect to the base of the underside of the trailer.
Figure 7 illustrates the above-described elements assembled and used as a
suspension system for a fixed axle trailer. Hanging bracket 100 is mounted on
the
underside of the trailer, and is pivotally connected to the support arm 102
through the use
of a bolt that serves as a pivot point through aperture 122 and mounting point
124. The air
bladder 104 is supported on the mounting surface 128, and supports the
underside of the
trailer to maintain a height roughly equivalent to the height of the hanging
bracket 100.
This keeps the trailer bed level, which is commonly desired. The support arm
102 is
fixedly connected to the axle 136, which has freely rotating wheels. The shock
absorber
106 is mounted on an angle between the mounting arm 102 and the hanging
bracket 100 to
aid the air bladder 104 in ensuring that oscillations caused by driving over
uneven surfaces
are dampened.
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Also shown in Figure 7 is an element of a sensor system used to determine if
the
trailer bed is maintained at a desired level. A connected pair of rods 149 is
connected to a
sensor 156. The pair of rods 149 is connected so that one of the rods is
parallel to the
support arm 102, and the other rod is fixedly mounted to either the support
ann 102 or the
axle 136. Sensor 156 is set to recognize an accepted neutral position,
preferably one where
the bed of the trailer is level. When the pressure in air bladder 104 is too
high, the trailer
bed will be lifted above the level position. This will exert a downward
pressure on the
support arm 102, and will increase the angle between the support arm 102 and
the hanger
bracket 100. This difference in angle will be mirrored in the connection of
the pair of rods
149 to the sensor 156. Similarly, when the pressure in air bladder 104 is
below the desired
level, angle between the support arm 102 and the hanger bracket 100 will be
decreased.
This decreased angle will be mirrored in the connection between the pair of
rods 149 to
the sensor 156. By detecting these differences in angles, sensor 156 can
control the
inflation and deflation of the air bladder 104. One skilled in the art will
appreciate that
this configuration is merely exemplary, and any number of other configurations
can be
employed, including the use of sensors that directly measure the distance
between the
support arm 102 and the trailer bed, or sensors that directly measure the
angle between the
support arm 102 and the hanger bracket 100. It should be noted that sensor 156
can be
described as a ride height sensor.
Figure 8 illustrates an exemplary embodiment of such a control system used on
a
trailer bed with multiple axles. One skilled in the art will appreciate that
an axle can be
supported by a pair of air bladders, and multiple axle trailers can be
accommodated by
increasing the number of bladder pairs. Multiple axles can be controlled using
a single
sensor system as illustrated in Figure 8, or can employ a multiple sensor
system, wherein
each axle is independently monitored. Those skilled in the art will appreciate
the
modifications to the control system that would be required are not
substantive, and can
also be accomplished through the use of multiple independent control systems.
Air
bladders 104 rely upon an air source, such as compressor 150, which draws
power from a
source 152 such as the vehicle that is towing the trailer. As noted earlier,
it is often
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possible to connect to a vehicle power system for such tasks as operating
marker lights. A
similar connection to power source 152 can be provided. In aiternate
embodiments, a
standalone power supply can be provided. The connection between power supply
152 ar.id
compressor 150 is made through regulator 154 which in conjunction with sensor
156
determines whether air pressure should be maintained or increased. Sensor 156,
in the
presently illustrated embodiment, can be implemented as a leveling valve that
can serve to
increase or decrease the pressure in the air bladders 104 as needed. If a
decrease in air
pressure is required, leveling valve 156, can provide air bladders 104 with
the means 'to
exhaust air by putting the bladders 104 in fluid communication with the
outside
environment, thus allowing the bladders 104 to vent. The exhausting of air can
be
continued until the desired trailer bed level is .reached and the leveling
valve 156 closes.
Between compressor 150 and the air bladders 104, is an air tank 160 that can
be
kept under pressure so that the inflation of the air bladders 104 can be
performed quicker
than would be possible if they were directly connected to air compressor 150.
When usirig
air tank 160, flow from the tank can be run through the sensor 156 to the dump
valve 158
(which can be implemented as a three way ball valve). In such a configuration,
the
leveling valve 156 has three states, an inflation state, a maintenance state
and a deflation
state. The choice of states is controlled by the ride height as determined by
leveling valve
156. The use of a single air passage to each of the air bladders 104 (though
both leveling
valve 156 and dump valve 158 for both inflation and deflation, which results
in an easier
to install system. Dump valve 158 can be used to provide the user with the
ability to
control the ride height of the trailer bed, or to control the air pressure in
tank 160 when the
system is powered down.
In operation, a sensor 156 determines whether the trailer bed is at the
desired level
(ride height). The bed can be at the level, in which case, no changes to the
air pressure in
the air bladders is needed; it can be too high, in which case the air bladders
104 need to be
deflated; or it can be too low in which case th.e air bladders 104 will need
to be inflated.
When sensor 156 determines the applicable state and selects between its three
states. In a
first state, a seal is effectively maintained, so that the air pressure in the
bladders 104 is
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maintained. In a second state, the bladders 104 are put into fluid
communication with the
air tank 160, which is at a higher pressure than the bladders 104. The air in
the system will
seek to find equilibrium, and thus will flow to the air bladders 104,
inflating them in the
process. When the desired level has been reached, the sensor 156 will seal
access to the
bladders 104. In the third state, the air bladders are put into fluid
communication with a
lower pressure environment, which can be done by opening a valve to the open
atmosphere. Once again, the air in the system will seek equilibrium, which in
this case will
empty the air bladders 104. In such a system the regulator 154 provides power
to the
compressor 150 from the power source 152 based on the air pressure in the tank
160.
Dump valve 158 can be used to provide manual control of the pressure in
various
components of the system. In standard operation, dump valve 158 allows the air
tank 1fi0
to be in fluid communication with the air bladders 104, a communication
controlled by
sensor 156. However, when in a powered off state, the user may want to lower
the bed of
the trailer which is achieved by venting the air bladders 104 to the
atmosphere. In such a
case, dump valve 158 can be used to empty the bladders 104. In some
embodiments, durnrp
valve 158 can also be used to vent pressurized air stored in tank 160 if so
desired.
Additional control elements including check valves, shut off valves and
couplers to
allow the pressure in the air tank to be released can be provided. The use of
these systems
will be well understood by those skilled in the art.
Numerous different types of sensors can be employed as sensor 156. In th.ie
illustrated embodiments, a leveling valve is employed to allow for the
creation of a simple
pneumatic control system. This valve can be preset so that there is a desired
level at which
the bed of the trailer is to be maintained. When the bed of the trailer is not
at this level, air
pressure in the bladders 104 is increased or decreased accordingly.
Optionally, an air
gauge 162 can be employed to measure the pressure in the suspension system,
which is
directly related to the pressure in bladders 104. Because the weight of the
trailer bed in
any given installation is constant, when the trailer bed is level the pressure
of the
suspension system is directly proportional to the weight of the load carried
by the trailer.
Thus an air gauge 162 can be employed to provide a rudimentary load scale on
the trailer.
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One skilled in the art will appreciate that by preventing pressurized air from
lillirig
the bladders 104, and using valve 158 to dump the air in the bladders 104, the
trailer bed
can be made to kneel. Because the trailer is typically supported at one end by
the trailer
hitch, lowering the level of the other end of the trailer by deflating the air
bladders 104 can
provide the kneeling functionality desired. To facilitate this change in the
control rules
used to level the trailer, an external controller interface 164 can be
employed in sorne
embodimerits of the present invention. The external controller interface 164
can allow the
user to deflate air bladders 104 without level sensor 156 triggering an
inflation cycle, and
it can allow the user to return the control system to a normal state and
elevate the trailer
bed from a kneeling position. Controller interface 164 can also provide the
user with the
ability to either pre-charge the air tank 160 or to evacuate the air tank 160
as desired.
Those skilled in the art will appreciate that there are a number of uses for
such an
interface, and that providing additional functionality through the user of an
external
interface controller 164 does not depart from the scope of the present
invention.
Though described above as using a mechanical control system regulated by a
leveling valve 156, the system of the present invention can be controlled
tlzrough the use
of an electronic control system that can be responsive to a number of
different inputs, such
as the height differential between the support arms 102 and the trailer bed,
the angle
between the hanger brackets 100 and the support arms 102, a direct measure of
the ricle
height, or a manual input such as one set through external controller
interface 164. Those
skilled in the art will appreciate that the implementation of such a system
does not depart
from the scope of the present invention.
The above-described embodiments of the present invention are intended to be
examples only. Alterations, modifications and variations may be effected to
the particular
embodiments by those of skill in the art without departing from the scope of
the inventio:n,
which is defined solely by the claims appended hereto.
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